Furnace for mills for hot rolling strips



Aug..31, 1937. J. K. SUTHERLAND FURNACE FOR MILLS FOR HOT ROLLING STRIPS Original Filed Aug. 6, 1935 INVENTOI? ATTORNEY Patented Aug. 31, 1937 STE PATENT OFFICE molten James 1K. Sutherland, Youngstown, Ohio Qriginal application August 6, 11935, Serial No.

Divided and this application Novemher 117, 1936, Serial No. 111,229

9 Claims.

This invention relates to the hot rolling of metal strips, the term strip being employed to designate any light gauge elongated piece of metal of any practicable width and not merely pieces of relatively narrow width which are sometimes referred to as strips.

This application is a division of my earlier application for U. S. Letters Patent, Serial No. 34,883, filed August 6, 1935, and is more particu- W larly directed to the apparatus therein disclosed as suitable for the performance of the method claimed in that application.

Various methods of and apparatus for reducing a slab or billet to form metal strips have heretofore been utilized, and one mill intended for this purpose comprises besides the usual roll table and reducing rolls, a heating chamber disposed adjacent and above each end of the table with the object of keeping the strip at a proper rolling temperature, and coiling mechanism is contained in each chamber so that as the strip is passed alternately between the rolls its leading end is coiled within one chamber as its trailing end is drawn out from the other. Necessarily each heating chamber or furnace is provided with an opening at or near the bottom to allow the strip to pass into and from the furnace and hence to and from the coiling mechanism, and it has been found in practice that these bottom openings permit frequent and relatively rapid changes in atmospheric conditions within the furnaces which result in irregular or spotty cooling of the strip and the reels on which it is coiled as well as variation in expansion and contraction of the parts. This not only causes pro-- duction of an unsatisfactory strip but also enhances the tendency of the reels and other parts of the coiling mechanism to break which renders maintenance costs, excessively high and impairs the productive emciencyof the apparatus as a whole.

It is therefore an object of my invention to remedy these disadvantages by the provision of a novel type of furnace adapted for operative association and combination with a mill for hot rolling strip whereby the temperature of the strip can be more satisfactorily controlled, difficulty incident to the use of reels or other coiling mechanism avoided, and production per hour en- 50 hanced through avoidance of the necessity for shutting down the mill to repair breakage or other deterioration due to temperature variations in the furnaces.

A further object of the invention is the pro- 55 vision of a furnace which when used in operative association and combination with a hot strip reversing mill avoids the use of reels and reeling mechanisms; which is designed for location below the level of the roll table of the mill and is of such character that the temperature within it can be controlled with great accuracy; which is simple in construction, and which comprises parts of a character not liable to get out of order or become damaged in operation in consequence of either temperature variations or any other cause.

The invention further includes other objects,

- advantages and novel features of design, construction and arrangement hereinafter more particularly pointed out or which will be apparent from the following description of a hot strip mill embodying a pair of my improved furnaces and illustrated in the accompanying drawing, in which Fig. l is a diagrammatic fragmentary top plan view of the mill and associated mechanism, and

Mg. 2 is a longitudinal central section thereof on the line 2-2 in Fig. l, the same characters of referenee'being used to designate the respective parts in both figures.

Essentially, the mill proper comprises a roll stand generally designated as R, that shown being of the four-high type embodying two relatively small working rolls W and a pair of considerably larger backing-up rolls B but if preferred a two or three-high mill may be utilized, or a mill of the cluster type, and hence the specific design of the rolls and roll stand are a matter of choice. The customary or any other suitable mechanism (not shown) is provided for driving the rolls and adjusting their position in the ordinary way so as to efiect the requisite reduction of the strip as it is passed between them.

On each side of the roll stand R at a convenient distance therefrom are disposed a pair of pinch rolls 1? with suitable driving means (not shown), and roll tables l, l of an ordinary type are interposed between the roll stand and each set of pinch rolls, while other tables 2; 2 extend oppositely outwardly from the latter. Longitudinal guides 35 supported from the tables by brackets G maintain the strip in proper position on the several tables during its passage thereover.

In accordance with-the present invention, adjacent and slightly beyond the outer ends of the tables 2 are located heating furnaces l0, Ill the refractory walls and bottoms of which may conveniently extend somewhat below the level of the work floor F, and as both furnaces and their associated mechanism hereinafter described are of similar construction, reference to one of them. for example the furnace ill at the right hand side of the drawing, will sufllce, the corresponding parts of the other furnace being designated by like numerals but with the addition of a prime The furnace I0 is preferably rectangular in horizontal section and wide enough, measured in a direction parallel to the axis of the rolls, to readily receive the Widest strip which themill is designed to produce. The preferably vertical side walls II and the bottom 12 of the furnace are desirably constructed of refractory material, the side walls being provided with vertical spaced guards 13 the purpose of which will hereafter appear, and the furnace top is open except for a movable guide cover I4 which, when closed down on the furnace top, lies just below the plane of the adjacent roll tables.

In order to maintain a suitable temperature within the furnace, horizontally disposed burners i5 adjacent its bottom are connected with a fuel pipe [6 through a controlling valve H. An additional similarly controlled pipe (not shown) for supplying air to each burner may be provided if desired, or a combustible mixture of gaseous fuel and air may be introduced through the pipes it, or any other convenient means may be employed to produce the requisite heating of the furnace.

The guide cover It to which reference has been made comprises a relatively thick curved cover plate horizontally hinged adjacent the top of the furnace and opening toward the roll stand. A crank arm 20 is secured to the cover for raising and lowering it on its hinges and is actuated from a fluid cylinder 2| the piston rod 22 of which is connected to the free end of the crank arm. The cylinder 2| is preferably mounted on horizontal trunnions 23 to permit slight oscillation during its operation, and a suitable actuating fluid is supplied through flexible connections 2 provided with control valves (not shown). This mechanism which I prefer to employ for raising and lowering the furnace cover is well adapted for its intended purpose, but of course any other convenient means for performing like functions may be utilized if desired.

The major part of the inner concave curved surface 25 of cover It conforms substantially to the convex curvature of its outer surface but its radius of curvature decreases rapidly adjacent its hinged inner edge before reversing to form the curved enlargement 26 through which is extended the shaft 21 hingedly supporting the cover.

On the under side of the cover adjacent its opposite or free edge suitable brackets 29 support a pair of spaced guide rolls 30, 3|, and an angular guide plate 32 is disposed between these rolls and the free edge to guide the strip to and between the rolls.

In the operation of the apparatus just described a billet or slab is first reduced to an elongated strip S by hot rolling between the working rolls in the usual way. Thus, the heated slab is brought to the mill from the heating furnace or other source along a roll table 35 to the right of furnace l0, and is then passed over the guide cover I4 which, with cover M of furnace i0, is maintained in lowered position during this period as indicated in dotted lines in Fig. 2. The slab is then introduced. to the mill rolls, the vertical spacing of the pinch and working rolls being of course properly adjusted for its passage therebetween under the desired pressure, and is then rolled back and forth between the working rolls until its reduction in thickness and resultant elongation render it of sufficient length to extend from the working rolls to or beyond the furnaces. When this point in the operation of the mill is reached, and preferably while an end of the strip is lying between the rolls and one furnace and therefore not above the cover of the latter, that cover is raised to the position shown in full lines in Fig. 2 so that during the next pass of the strip its leading end is guided by the raised furnace cover and attached mechanism into the subjacent furnace. After the trailing end of the strip clears the other furnace cover on this pass the latter is also raised and thereafter the ends of the strip are thus successively directed into the adjacent furnaces on successive passes in oppositely directed folds or layers as indicated in Fig.2, guards i3, i3 preventing it from contacting the furnace walls and causing undue abrasion of the refractory material of which they are constructed.

The strip is thus maintained at elevated temperature by the furnaces throughout the rolling operation, its major portion, after the preliminary reduction and elongation, being passed back and forth from one furnace to the other while the portions adjacent its ends are drawn from their respectively corresponding furnaces, rolled in both directions and promptly returned, and all portions of the strip are consequently prevented from falling below proper rolling temperature.

After the strip has been sufficiently elongated and reduced to the desired thickness, the cover of furnace i0 is lowered upon withdrawal of the adjacent end of the strip therefrom during its last pass from left to right in Fig. 2 and on the final pass in the opposite direction this end of the strip then moves over the cover of furnace iii onto the roll table 36 to the left thereof which conducts the strip to a coiler, continuous pickling machine or other apparatus for whatever further treatment, if any, is desired.

It results that the strip is maintained at proper rolling temperature throughout the rolling operation, and by suitable regulation of the furnace heating means this temperature may be readily controlled and adjusted to the strip thickness, rolling speed and other determining factors. Moreover, all portions of the strip are in one furnace or the other a relatively large percentage of the time during which rolling is in progress, being withdrawn therefrom only just prior to being acted upon by the working rolls and thereafter rapidly passed to the other furnace or returned to the same one, as the case may be, the end portions of the strip of course being only passed back and forth between the rolls and their respectively adjacent furnaces. Appreciable loss of heat from the strip. its unequal cooling and/or heating and/or that of the mechanisms with which it is associated are thereby avoided, the productive efficiency of the mill materially enhanced and its operative life prolonged.

Additionally, as the strip is introduced into each furnace it is bent back and forth in opposite directions along longitudinally spaced transverse lines, and any scale which may adhere to its surfaces is thereby loosened and cracked off. The folds are substantially uniformly spaced longitudinally of the strip at distances determined primarily by the width of the furnace but elongation of the strip during each pass prevents excessive bending of any portion of the Strip r ugh shifting the metal relatively to the points at which the folds are made. During reduction of a slab to relatively thin strip substantially all portions thereof are severally subjected to this bending or folding action to some extent, and the finished strip is therefore virtually scalefree and is possessed of a substantially uniform grain structure in consequence of the combined rolling and bending operations performed upon it during its reduction, while the openness of the folds, as distinguished from the close contact of adjacent convolutions when the strip is coiled, insures uniform heating of the strip throughout its entire extent.

While I have herein described with considerable particularity one form of apparatus constructed in accordance with the invention, it will be understood that the latter is not to be considered as confined or restricted thereto as various modifications such as will readily occur to those skilled in the art may be made in the form, construction and arrangement of the various parts if desired without departing from the spirit and scope of the invention as defined in the appended claims.

Having thus described my invention, I claim and desire to protect by Letters Patent of the United States:

1. In combination with horizontal strip supporting means, a furnace providing a heating chamber disposed below the working plane of said means and comprising side and end walls, a bottom and a hinged cover adapted for projection into said working plane and operable to deflect the leading end of a strip into said chamber, and means for moving said cover to open and closed positions.

2. In combination with strip supporting means, a furnace disposed below the working plane of said means comprising side and end walls and a bottom, heating means disposed in the furnace, a movable cover overlying the top of the furnace and adapted for projection into the working plane of said supporting means, guide means carried by the cover operative to intercept a strip carried by said supporting means, and means for raising and lowering the cover.

3. A strip heating furnace comprising a bottom, side andend Walls, heating means for the furnace, guards positioned adjacent the side walls adapted to maintain a strip in spaced relation thereto when disposed in the furnace, and a movable cover for the furnace operative to enter the strip into the furnace when the strip is moved in one direction relatively to the cover and in engagement therewith.

4. A strip heating furnace comprising side and end walls, a bottom, a hinged cover therefor, and guide means carried by the cover adapted to bend a moving strip and thereby direct it into the furnace.

5. A strip heating furnace comprising refractory side and end walls and a bottom, a. hinged cover for the furnace having a concave inner surface adapted to deflect into the furnace a moving strip brought into contact therewith, a

, guide plate and a pair of guide rolls carried by the cover cooperative to guide the moving strip into engagement with said surface.

6. In combination with means adapted to progressively move a strip in a substantially horizontal path, a furnace providing a heating chambe disposed below said path, and a cover for said chamber movable from closed position wherein all of its parts are disposed below said path to a position in which it intersects said path to thereby deflect the strip into the subjacent heating chamber when it is traveling toward the cover. 7. In combination with means for supporting and progressively moving a strip in a substantially horizontal path, a furnace disposed below said path and providing a heating chamber open at the top and having side and end walls and a bottom, and a cover adapted to close the top of the chamber and vertically movable between open and closed positions about a horizontal axis transverse to the direction of travel of the strip, said cover when closed lying wholly beneath said path and when open intersecting said path to thereby divert the strip into the subjacent chamher when it is moved toward the cover.

8. In combination with means for supporting and progressively moving a strip in a substantiab ly horizontal path, a furnace disposed beneath V said path and providing a heating chamber, a

cover having a concave under surface and hinged adjacent the top of the furnace adapted to close the top of the chamber when lowered and to intersect said path when raised, and means on the under side of the cover operative to direct the strip against its concave surface when the strip is progressively moved toward the raised cover to thereby direct the strip downwardly into the subjacent furnace.

9. In combination with means for supporting and progressively moving a strip in a substantially horizontal path, a heating furnace disposed adjacent said path below the plane thereof, and

a cover for the furnace hinged on an axis transverse to said path for vertical movement between raised and lowered positions, the cover being adapted when lowered to close the furnace and lie wholly beneathsaid path and when raised to open the furnace and intersect said path to thereby divert the strip downwardly into the furnace when the strip is moving toward the cover.

JAMES K. SUTHERLAND. 

